Convenient synthesis of naphthopyrans using montmorillonite K-10 as heterogeneous catalyst

Abstract

A simple and mild procedure for the synthesis of different naphthopyrans providing high yields in a short reaction time was reported. The reaction of propargylic alcohols with α- or β-naphthol and dihydroxy naphthalenes in the presence of montmorillonite K-10 was studied. This reaction afforded high yields of the corresponding naphthopyrans. In addition, a number of new phenylene and biphenylen-linked bisnaphthopyrans were synthesized providing excellent yields via the one-pot reaction of bis-propargyl alcohols with β-naphthol. A simple, mild and efficient procedure for the synthesis of different naphthopyrans including novel naphthopyrans with fluorene and ferrocene moieties is reported. The reaction of propargylic alcohols with α-or β-naphthol and dihydroxy naphthalenes in the presence of montmorillonite K-10 was studied and afforded high yields of the corresponding naphthopyrans.